Quantico, Virginia - President Donald Trump laced into FBI leadership Friday, while proclaiming his loyalty and support for law enforcement in an address at the agency's training academy.

"It's a shame what's happened" with the FBI, the president said as he left the White House for a speech at the FBI training academy in Quantico, Virginia. He called the agency's handling of Hillary Clinton's email investigation "really disgraceful" and told reporters "we're going to rebuild the FBI."

Shortly afterward, Trump lavished praise on graduates of a weeks-long FBI National Academy program and their families, touting their accomplishments and pledging his unwavering support. Trump told law enforcement leaders he is "more loyal than anyone else could be" to police.

"Anti-police sentiment is wrong and it's dangerous," he added. "Anyone who kills a police officer should get the death penalty."

Trump used the speech to promote his administration's tough-on-crime policies, delivering a stern warning to members of the international gang MS-13 that his administration will root them out and arrest them.

He also celebrated his decision to make it easier for local police forces to purchase surplus military equipment, and questioned rising violence in Chicago.

"What the hell is going on in Chicago? What the hell is happening there," he asked.

Parts of a letter written by Senator Ron Johnson, R-Wis., to FBI director Christopher Wray are photographed in Washington. Picture: Jon Elswick/AP

"There is extreme bias against this president with high-up members of the team there at the FBI who were investigating Hillary Clinton at the time," Gidley charged, as special counsel Robert Mueller pushes on with a probe of possible Trump campaign ties to Russia. Gidley says Trump maintains confidence in the FBI's rank-and-file.

Edits to the Comey draft appeared to soften the gravity of the bureau's finding in its 2016 investigation of Hillary Clinton's use of a private email server while secretary of state.

"It is very sad when you look at those documents, how they've done that is really, really disgraceful, and you have a lot of really angry people who are seeing it," Trump said of the document.

President Donald Trump gestures to the crowd at the FBI National Academy graduation ceremony in Quantico, Virginia. Trump said "it's a shame what's happened" with the FBI, calling the agency's handling of the Hillary Clinton email investigation "really disgraceful." Picture: Evan Vucci/AP

Gidley said the disclosure of politically charged text messages sent by one of the agents on the Clinton case, Peter Strzok, were "eye-opening." Strzok, who was in the room as Clinton was interviewed, was later assigned to special counsel Robert Mueller's team to investigate potential coordination between Russia and the Trump campaign. He was re-assigned after the messages were uncovered this summer.

About 200 leaders in law enforcement from around the country attended the weeks-long FBI National Academy program aimed at raising law enforcement standards and cooperation. Coursework included intelligence theory, terrorism and terrorist mindsets, law, behavioral science, law enforcement communication, and forensic science.